Direct Numerical Simulation of Supersonic Turbulent Boundary Layer Flow

Direct numerical simulations of a spatially evolving supersonic flat-plate turbulent boundary layer flow with free Mach number M = 2.25 and Reynolds number Re = 365000/in are performed. The transition process from laminar to turbulent flow is obtained by solving the three-dimensional compressible Navier-Stokes, equations, using high-order accurate difference schemes. The obtained statistical results agree well with the experimental and theoretical data. From the numerical results it can be seen that the transition process under the considered conditions is the process which skips the Tolimien-Schlichting instability and the second instability through the instability of high gradient shear layer and becomes of laminar flow breakdown. This means that the transition process is a bypass-type transition process. The spanwise asymmetry of the disturbance locally upstream imposed is important to induce the bypass-type transition. Furthermore, with increasing the time disturbance frequency the transition will delay. When the time disturbance frequency is large enough, the transition will disappear.

Undercooling and Rapid Solidification of Nb-Si Eutectic Alloys Studied by Long Drop Tube

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

Experimental Investigation On The Holdup Distribution Of Oil-Water Two-Phase Flow In Horizontal Parallel Tubes

An experimental investigation was conducted to study the holdup distribution of oil and water two-phase flow in two parallel tubes with unequal tube diameter. Tests were performed using white oil (of viscosity 52 mPa s and density 860 kg/m(3)) and tap water as liquid phases at room temperature and atmospheric outlet pressure. Measurements were taken of water flow rates from 0.5 to 12.5 m(3)/h and input oil volume fractions from 3 to 94 %. Results showed that there were different flow pattern maps between the run and bypass tubes when oil-water two-phase flow is found in the parallel tubes. At low input fluid flow rates, a large deviation could be found on the average oil holdup between the bypass and the run tubes. However, with increased input oil fraction at constant water flow rate, the holdup at the bypass tube became close to that at the run tube. Furthermore, experimental data showed that there was no significant variation in flow pattern and holdup between the run and main tubes. In order to calculate the holdup in the form of segregated flow, the drift flux model has been used here.

Undercooling and Rapid Solidification of Nb-Si Eutectic Alloys Studied by Long Drop Tube

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

沿平板可压缩湍流边界层的直接数值模拟

湍流广泛存在于自然界和工程应用中。可压平板湍流是一种典型的壁湍流，对其进行直接数值模拟研究是壁湍流机理研究的基础。本文采用高精度紧致型差分格式求解三维可压N-S方程，利用MPI并行程序，直接数值模拟了来流马赫数为M的＝2．25，雷诺数为Re＝635O00／in．的空间发展的可压缩平板湍流边界层。本文主要研究了如下一些问题。方法研究方面：●针对壁湍流流动的特点，文中提出了与基于非等距网格高精度紧致型差分格式相结合的简化的迭代一隐式时间推进法，建立了可压缩平板湍流边界层直接数值模拟方法。提高了计算效率，并给出了迭代收敛的条件。●研究了不同网格加密方法对数值解分辨率的影响，指出在保证近物面附近物理平面内网格是均匀的条件下，采用坐标变换的方法也可得到近物面高分辨率的数值解，纠正了人们认为只有在基于非等距网格上才能得到高分辨率解的观点。●采用包括前缘在内的二维可压平板层流边界层直接数值模拟结果为三维可压平板湍流边界层计算提供上游边界条件，解决了国外采用的局限性很大的经验公式带来的不相容问题。物理问题的模拟研究：●在国内首次给出了超声速平板边界层从层流经bypass转披直到充分发展湍流的整个过程。所得流场统计特征（如平均速度分布，物面摩阻系数，脉动速度的均方根等）与相关理论和实验符合甚好。这些结果充分证实了本文所建立的数值方法的有效性和所得结果的可靠性。●在此基础上，文中分析了可压平板湍流边界层内的拟序结构的形成过程。研究了初始扰动对平板边界层流动转挨特征的影响，指出上游初始扰动中展向的非对称性是形成bypass转挨的关键因素，且较大的时间扰动频率使得边界层转披位置后移。这些结果为壁湍流控制提供一定依据。●在此基础上研究了可压缩效应对平均流动特征以及湍能的生成和耗散特征的影响，指出在Mc∞=2.25的情况下，Morkovin假设基本成立。但可压缩效应使得边界层内层中过渡层加宽；拟序结构有明显差别。与不可压相比上抛、下扫对不同区域的作用有所不同。在近壁区，湍动能方程中的压力-膨胀项和压力-速度相关项仍是不可忽略的量，这导致声的产生和可压缩效应对湍流的发展所产生的抑制作用。

Detour behavior changes associated with prenatal morphine exposure in 11-day-old chicks

The central nervous system exhibits remarkable plasticity in early life. Prenatal morphine exposure may induce adverse behavioral effects on the neonate and the developing offspring. In the present study, we investigated the effect of prenatal morphine exposure (daily from embryonic days 12-16, 20 mg/kg) on 11-day-old chicks using two forms of spatial paradigms: one trial detour behavior task in which animals must bypass an obstacle to reach the desired goal without any training and detour learning task which required several trials of training to reach the detour criterion. The results showed that, on the condition that chicks could successfully detour in the first trial, morphine exposed chicks exhibited longer detour latency to finish the task, coupled by a preference for turning right versus turning left. In contrast, no significant difference in learning and memory was found in detour learning task between morphine exposed chicks and saline chicks. These findings suggest specific behavioral changes associated with prenatal exposure to opioids during mid to late gestation, also raise attention to the possible health hazard from pregnancy drug use in everyday life. (C) 2010 ISDN. Published by Elsevier Ltd. All rights reserved.

Monolithic optical gates based on integration of evanescently-coupled uni-traveling-carrier photodiodes and electroabsorption modulators

We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photodiodes (EC-UTC-PDs) and intra-step quantum well electroabsorption modulators (IQW-EAMs) on n-InP substrates. These devices exhibit simultaneously 2.1 GHz and -16.2 dB RF-gain at 21 GHz with a 450 Omega thin-film resistor and a bypass capacitor integrated on a chip.

CFD analysis of pneumatic conveying in a double-tube-socket (DTS (R)) pipe

A pipeline with a bypass is widely used for the pneumatic conveying of material. The double-tube-socket (DTS (R)) technology, which uses a special inner bypass, represents the current state of the art. Here, a new methodology is proposed based on the use of computational fluid dynamics (CFD) to predict the energy consumption of DTS conveying. The predicted results are in good agreement with those from pilot-scale experiments. (C) 2010 Elsevier Inc. All rights reserved.

Direct formation of form I poly(1-butene) single crystals from melt crystallization in ultrathin films

The morphologies and crystalline structures of melt-crystallized ultrathin isotactic poly(1-butene) films have been studied with transmission electron microscopy and electron diffraction. It is demonstrated that a bypass of form II crystallization can be achieved with an increase in its crystallization temperature. Electron microscopy observations show that melt-grown isotactic poly(1-butene) single crystals have a well-shaped hexagonal form, whereas form I crystals converted from form II display the morphologies of their tetragonal precursors. Electron diffraction results indicate that, instead of the twinned hexagonal pattern of the converted form I crystal, the directly formed form I single crystals exhibit an untwinned hexagonal pattern.

冠状动脉旁路移植术后抑郁焦虑状态随访和分析

To explore the presence of depression, anxiety and cardiac events after coronary artery bypass grafting (CABG) prospectively and comparably. To analysis influential factors of depression and anxiety ( peri-operation and 1 year after operation ), and the effection on cardiac events in the year after operation. We followed the patients who underwent scheduled consecutive CABG. We interviewed patients to assess depression, anxiety symptoms using self-rating depression scale( SDS) and self-rating anxiety scale（SAS）before operation , before discharge and 1 year after operation. And cardiac events were also identified. All patients were divided into the group with depression and/or anxiety symptoms or the other group without depression and/or anxiety symptoms 3 times according to depression and anxiety symptoms before operation , before discharge and 1 year after operation. 69 patients completed the follow-up.24 patients (34.8%) had depression and/or anxiety symptoms before CABG, 31 patients (44.9%) had depression and/or anxiety symptoms before discharge, and 10 patients (14.5%) had depression and/or anxiety symptoms 1 year after operation. 6 patients(8.7%) had cardiac events, and 5 patients were re-admitted. Arhythmia before and after operation, the quantity of blood vessel grafted, length of stay , depression and anxiety symptoms before operation, cardiac events may lead to depression and anxiety symptoms 1 year after operation. The use of cardiopulmonary bypass grafting (CPB), Arhythmia after operation, the prolonged length of stay are influential factors of cardiac events. Though the incidence of depression and/or anxiety symptoms 1 year after operation is lower than before operation and before discharge, it is high still. Arhythmia before and after operation, the more blood vessels grafted, the prolonged length of stay , depression and anxiety symptoms before operation and cardiac events could be risk factors of depression and anxiety symptoms 1 year after operation. Much attention must be paid to this phenomenon. Heavy patient's condition, complicated surgery are risk factors of cardiac events, and bad emotion before operation and before discharge are independent to cardiac events. Key words： perspective research; depression；anxiety; coronary artery bypass grafting; follow up

Protocol of capillary isoelectric focusing to separate extremely acidic and basic proteins

A new set-up was constructed for capillary isoelectric focusing (CIEF) involving a sampling capillary as a bypass fixed to the separation capillary. Sample solutions were subjected to a previously established pH gradient from the sample capillary. Besides performing conventional CIEF, the separation of ampholytic compounds with isoelectric points (p/s) beyond the pH gradient was carried out on this system. This method was termed as pH gradient driven electrophoresis (PGDE) and the basic mathematical expressions were derived to express the dynamic fundamentals. Proteins such as lysozyme, cytochrome C, and pepsin with p/s higher than 10 or below 3 were separated in a pH gradient provided by Pharmalyte (pH 3-10). Finally, this protocol convincingly exhibited its potential in the separation of a solution of chicken egg white.